Unity - The multiplatform game creation tools for everyone.
Godot Engine - Feature-packed 2D and 3D open source game engine.
GDevelop - GDevelop is an open-source game making software designed to be used by everyone.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Stencyl - Make iOS (iPhone/iPad), Android, Flash, Windows & Mac games without code using Stencyl.
CryENGINE - The most powerful game development platform is now available to everyone. Full engine source code.